The present invention relates to a prober for examining the electric characteristics of an electronic element by use of a probe card that has probes arranged in accordance with the arrangement of the electrodes of the electronic element, and specifically to a mechanism for attaching the probe card to the prober.
To be more specific, the present invention is directed to a mechanism for attaching a probe card to a prober designed to examine the electric characteristics of an integrated circuit formed on a semiconductor wafer.
The present invention will be described below, referring to the case where it is applied to a prober designed for examining an integrated circuit on a wafer, but the invention is in no way limited to such a case. That is, the present invention is applicable to all types of probers that are designed for examining the electric characteristics of various electronic elements (objects to be examined) by use of a probe card. In other words, the present invention is not limited to a mechanism for attaching a probe card to a prober that is merely designed for checking an integrated circuit on a semiconductor wafer.
An example of a conventional prober for checking an integrated circuit formed on a wafer is shown in FIG. 7. As shown in this FIGURE, the conventional prober comprises: a casing 11; a susceptor 12, arranged inside the casing 11 and movable in X-, Y-, Z- and .theta.-directions, for holding a wafer W to be checked; a probe card 13 having probes 13A arranged in correspondence to the electrode pads of integrated circuits formed on the wafer W on the susceptor 12; an insert ring 15 used for securing the probe card 13 to a card holder 14; and a connection ring 16 for electrically connecting the probe card 13 secured by means of the insert ring to a test head 17. The electrode pads of the integrated circuits on the wafer W are positioned with reference to the corresponding probes 13A by adjusting the position of the susceptor 12. Subsequently, the integrated circuits are electrically examined by exchanging test signals between a tester (not shown) and the integrated circuits through the probe card 13, the connection ring 16 and the test head 17.
The probe card 13 can be replaced with another in an automatic or semiautomatic fashion. For this replacement, the insert ring 15 is provided with an automatic or semiautomatic probe card attaching mechanism (hereinafter referred to simply as a attaching mechanism). By this attaching mechanism, the probe card 13 is fitted to a clamp and removed therefrom.
The attaching mechanism has such a structure as is shown in FIG. 8. This FIGURE is an enlarged view showing details of the portion that is inside the circle indicated in FIG. 7. As shown in FIG. 8, the attaching mechanism comprises a fixing ring 151 secured at an opening of a head plate 11A, a cylinder ring 152 fitted with the lower side of the fixing ring 151 and having an annular groove formed throughout the circumference of the upper side thereof, and an O-ring 154 fitted in the annular groove to define an airtight chamber 153. A piston ring 155 is vertically movable along the outer face of the cylinder ring 152. The piston ring 155 has a flange 155A, and this flange 155A pushes the O-ring 154. A card-receiving ring 156 engages with the outer surface of the piston ring 155 and is rotatable in the circumferential direction.
The card-receiving ring 156 has a plurality of engagement sections 156A on the inner circumferential surface thereof. The engagement sections 156A are arranged at equal intervals in the circumferential direction and are projected radially inward. The card holder 14 has a plurality of engagement sections 14A on the outer circumferential surface thereof. The engagement sections 14 are arranged at equal intervals in the circumferential direction and projected radially outward. Each of the engagement sections 14A of the card holder 14 is located between the corresponding engagement sections 156A of the card-receiving ring 156. When the card-receiving ring 156 rotates in the circumferential direction, its engagement sections 156A are brought into engagement with the corresponding engagement sections 14A, thereby permitting the card-receiving ring 156 to hold the card holder 14.
A passage 157 for allowing communication between the airtight chamber 153 and an outside region is defined. As shown in FIG. 8, the passage extends along the fixing ring 151 and the cylinder ring 152. An air supply source (not shown) is connected to the passage 157. From the air supply source, compressed air is supplied through the passage 157 into the airtight chamber 153. When the compressed air is supplied into the airtight chamber 153, the pneumatic pressure raises the O-ring 154 together with the piston ring 155, thereby permitting the card ring 156 and the cylinder ring 152 to hold the card holder 14 in the fitted state. For automatic or semiautomatic replacement of the probe card 13, the compressed air is discharged from the airtight chamber 153. Since the piston ring 155 is lowered together with the card ring 156, the card holder 14 is separated from the cylinder ring 152. In this state, the card-receiving ring 156 is rotated, thereby releasing the engagement between the engagement sections 14A of the card holder 14 and the engagement sections 156A of the card-receiving ring 156. Accordingly, the probe card 13 becomes ready for replacement.
In the conventional proper described above, the insert ring 15 constitutes a attaching mechanism. The attaching mechanism 15 raises the piston ring 155 and the card holder 14 by utilization of the pneumatic pressure in the airtight chamber 153 of the cylinder ring 152, and the probe card 13 is fitted and held by the lower side of the cylinder ring 152 and the card-receiving ring 156. With the attaching mechanism, it is hard to lift the probe card 13 exactly in the vertical direction. In other words, the probe card 13 is likely to slant though slightly when it is being lifted. The probe card 13 does not slant greatly if it is the one designed for examining a wafer whose diameter is in the range of 6 to 8 inches. However, the probe card 13 does slant greatly if it is for examining a large-diameter wafer (e.g., a 12" wafer) since such a probe card is also large in diameter. If a large-diameter probe card slants, it may touch pogopins. That is, the pogopins on the lower side of the connection ring 16 may not be in uniform contact with the terminals of the probe card 13. If this occurs, the pogopins is applied with an overload and may be damaged. In addition, some of the pogopins may not be in reliable contact with the probe card 13, and the test may not be executed in a satisfactory manner.